Well just in case they dont know what linux is let me sum up: In the computer world there is big debate between PC vs Mac, PC referring to computers using Windows and Mac referring to apple based computers with OSX. Linux is an alternative to both, offering an alternative to both the above. Linux is a kernel, the core of a OS thus why if you look up linux you see so many names crop up. Also its open source meaning its not a closed off system like windows or OSX. Now just in case you dont know what open source is, open source is a term to describe software not bogged down by some big company, instead its code anyone can modify and or use. You may wonder "well it must be insecure then!" no because the code is open you can make open source software ten times more secure then closed source ones. Of course exploits do happen. Anyhow Linux is the most popular OS outside of the main 2, and yes if you are using android you are using linux as android is based off linux.